Comprehensive Monograph on Fostamatinib (DB12010)

Executive Summary and Key Insights

Fostamatinib is a first-in-class, orally administered small molecule that functions as a prodrug for its active metabolite, R406.[1] R406 is a potent and selective inhibitor of Spleen Tyrosine Kinase (Syk), a critical enzyme in the intracellular signaling pathways of various immune cells.[3] Marketed under the brand names Tavalisse in the United States and Tavlesse in Europe, fostamatinib is approved for the treatment of adult patients with chronic immune thrombocytopenia (ITP) who have had an insufficient response to previous therapies.[3] Its primary mechanism of action involves the inhibition of Fc receptor-mediated phagocytosis of antibody-coated platelets by macrophages, a novel therapeutic approach that directly targets a key pathological process in ITP.[3]

The clinical efficacy of fostamatinib in refractory ITP has been established through a pivotal Phase 3 program. While the overall rate of stable platelet response is modest, the data from two placebo-controlled trials and a long-term extension study demonstrate a statistically significant and clinically meaningful benefit for a difficult-to-treat patient population.[10] For patients who do respond, the increase in platelet count is often rapid, occurring within weeks of initiation, and has been shown to be durable with continued treatment.[11]